Many analytic systems incorporate valves for controlling fluid flow. An example is the use of shear valves in some chromatography systems. These valves often must retain fluid integrity, that is, such valves should not leak fluids. As a valve is cycled, however, between positions, the loads placed on the moving parts cause wear.
Some valves are subjected to high pressures. For example, sample injector valves in high performance liquid chromatography (HPLC) apparatus, are exposed to pressures approximately 1,000 to 5,000 pounds per square inch (psi), as produced by common solvent pumps. Higher pressure chromatography apparatus, such as ultra high performance liquid chromatography (UHPLC) apparatus, have solvent pumps that operate at pressures up to 15,000 psi or greater.
As the pressure of a system increases, wear and distortion of a valves components, such as a rotor and a stator, tends to increase, and the valve's expected lifetime may be reduced.